(HealthDay News) — Obese women taking oral contraceptives may be nearly 30 times more likely to develop cerebral venous thrombosis (CVT), compared with women of normal weight who do not take birth control pills, according to a study published in JAMA Neurology.

The study included 186 adult CVT patients, including men and women. Their strokes occurred from the mid-2000s through December 31, 2014. The study also included a control group of 6134 healthy adults. These adults had taken part in a large Dutch study conducted from 1999 to 2004. That study looked at risk factors for deep vein thrombosis and pulmonary embolism.

The researchers found that CVT patients were more often younger. Their median age was 40 compared with 48 for the control group. They were also more likely to have a history of cancer. Additionally, they were more likely to be female and users of oral contraceptives.

Obesity was associated with a nearly 30-fold increased risk of CVT, but only among women using oral contraceptives.

In a related editorial, Chirantan Banerjee, MD, MPH, of the Medical University of South Carolina in Charleston, said that better counseling of obese women, including consideration of non-hormonal contraceptive options, “would be prudent.”